1. Field of the Invention
The present invention relates to a conductive film, a touch panel and a display device including the conductive film, and a conductive film evaluation method, and more particularly, to a conductive film having mesh pattern wires that is excellent regarding the visibility of moire and noise in the design of a mesh wiring pattern (hereinafter, referred to as a mesh pattern) in which a plurality of opening portions (cells) are formed by a plurality of thin metal wires, a touch panel and a display device including the conductive film, and a conductive film evaluation method.
2. Description of the Related Art
For example, a conductive film for shielding electromagnetic waves or a conductive film for a touch panel is given as an example of a conductive film which is provided on a display unit of a display device (hereinafter also referred to as a “display”) (for example, see JP2009-117683A, JP2011-216379A, and JP2011-517355A).
When an object (for example, a finger) presses a surface of a touch panel, the pressed position is detected by a conductive film (sensor). The conductive film (sensor) includes a first conductive portion (electrode) and a second conductive portion (electrode) which extend in directions perpendicular to each other.
In general, an insulating transparent base is interposed between the first conductive portion and the second conductive portion.
The first conductive portion and the second conductive portion have a mesh pattern which is formed by crossing thin metal wires (wire rods). An opening portion (space) surrounded by the thin metal wires which intersect each other is also called a cell. In general, the cell has a polygonal shape or an irregular shape.
When the cells have the same predetermined shape, such as a rectangular shape, the mesh pattern is generally a regular wiring pattern, that is, a fixed pattern in which a plurality of cells having the same shape are continuously repeated. It is known that moire (interference fringe) is likely to be generated by the interference between the regular wiring pattern and a pixel array pattern (for example, a black matrix (hereinafter, referred to as a BM pattern)) of the display.
When the cells have an irregular shape or various shapes, there is no regularity (uniformity) in the shapes of the cells and the mesh pattern is generally an irregular wiring pattern, that is, a random pattern since it is difficult to repeatedly arrange cells with the same shape. It is known that, in a random pattern, a granular feeling of noise (a feeling of roughness) is likely to be perceived and transmittance is lower than that in a fixed pattern.
JP2009-117683A filed by the inventors discloses a technique which automatically selects a wiring pattern generated by wiring pattern data in which the relative distance (for example, corresponding to the frequency of moire) between the spectrum peaks of a two-dimensional Fourier spectrum (2DFFTSp) of pattern data of each of a pixel array pattern, such as a BM pattern, of a display and a wiring pattern, such as an electromagnetic wave shielding pattern, is more than a predetermined spatial frequency, for example, 8 cm−1.
In addition, JP2009-117683A discloses a technique which, when the relative distance is not more than the predetermined spatial frequency, repeatedly performs a process of changing at least one of a rotation angle, a pitch, and a pattern width of the wiring pattern data to generate new wiring pattern data until the relative distance is more than the predetermined spatial frequency.
In JP2009-117683A, the relative distance (the frequency of moire) between the spectrum peaks of the pixel array pattern and the wiring pattern, for example, the BM pattern in which predetermined pixels are regularly repeated and the regular wiring pattern (see FIGS. 2 and 6) is more than the predetermined spatial frequency. According to this structure, it is possible to automatically select an electromagnetic wave shielding pattern which can suppress the generation of moire and avoid an increase in surface resistivity or the deterioration of transparency.
JP2011-216379A filed by the inventors discloses a transparent conductive film in which a mesh pattern (for example, a random pattern: see FIGS. 2 and 14) including a plurality of polygonal meshes is formed such that the average intensity of the centroid spectrums of each mesh in a spatial frequency band higher than a predetermined spatial frequency, for example, a spatial frequency at which a human visual response characteristic corresponds to 5% of the maximum response is higher than that in a spatial frequency band lower than the predetermined spatial frequency.
Therefore, in JP2011-216379A, it is possible to provide a transparent conductive film which can reduce the granular feeling of noise caused by the random pattern, can significantly improve the visibility of the object to be observed, and has a stable conduction performance even after being cut.
JP2011-517355A discloses a technique in which the width of a conductive micro-pattern element, such as a regular mesh pattern (for example, see FIG. 2, FIG. 11, and FIG. 25) or a random pattern (see FIG. 23) including random-shaped cells is reduced to 1 μm to 10 μm such that the conductive micro-pattern element is less likely to be seen and a structure for obscuring the conductive micro-pattern element or reducing the visibility of the conductive micro-pattern element is provided such that the conductive micro-pattern element is less likely to be seen. JP2011-517355A also discloses a pseudo random change in the conductive micro-pattern as an example of the structure.